Instrument for testing operability of fluorescent lamps

ABSTRACT

An instrument for testing fluorescent lamps including a tubular housing in which is incorporated a high frequency oscillator circuit and a tank coil in said circuit producing an inductive effect to cause a fluorescent lamp to light up when in close proximity thereto. The instrument is capable of testing two types of fluorescent lamps commonly in use, one type utilizing cathodes in the form of coated wire filaments which must be continuously heated by an electric current passing through them from auxiliary energizing equipment. The instrument includes a socket for plugin attachment of such lamps, a portion of the tank coil surrounding an end of the tube when it is plugged in for causing the lamp to light if not defective. The other type of fluorescent lamp in common use is a single pin lamp which does not depend on cathodes heated from an external source for its proper operation. While testing the latter type of lamp, the instrument is merely placed endwise in close proximity to any portion of the tube between its ends to cause the tube to light up if not defective.

United States Patent Masengil Aug. 29, 1972 [541 INSTRUMENT FOR TESTING PririiaryExaminer-Rudolph v. Rolinec OPERABILITY OF FLUORESCENT Assistant Examiner-David M. Carter LAMPS Attorney-Eugene M. Eckelman [72] Inventor: Verdie A. Masengil, 1500 McClay [57] Drive, Eugene, Oreg. 97402 22 Filed: Oct. 22, 1970 21 Appl.No.: 83,087

52 us. Cl .324/22, 324 33 51 lnt.Cl. ..G01l' 31/22 [58] Field of Search ..324/20-27, 33, a 324/61 Tl, 340sc; 331/44 [56] References Cited UNITED STATES PATENTS 2,497,525 2/1950 Zyta ..324/22 2,633,486 3/1953 Sweet ..324/33 OTHER PUBLICATIONS L. Dezettel, The Grid Dip Meter, Electronics World, Dec. 1960, 50 & 51.

An instrument for testing fluorescent lamps including a tubular housing in which is incorporated a high frequency oscillator circuit and a tank coil in said circuit producing an inductive effect to cause a fluorescent lamp to light up when in close proximity thereto. The instrument is capable of testing two types of fluorescent lamps commonly in use, one type utilizing cathodes in the form of coated wire filaments which must be continuously heated by an electric current passing through them from auxiliary energizing equipment.- The instrument includes a socket for plugin attachment of such lamps, a portionof the tank coil surrounding an end of the tube when it is plugged in e for causing the lamp to light if not defective. The

other type of fluorescent lamp in common use is a single pin lamp which does not depend on cathodes heated from an external source for its proper operation. While testing the latter type of lamp, the instrument is merely placed endwise in close proximity to any portion of the tube between its ends to cause the tube to light up if not defective.

PATENTED M1829 IQIZ' Ill! ERDIE A. MASENGIL Qm g xTOR.

ATTY.

INSTRUMENT FOR TESTING OPERABILITY OF FLUORESCENT LAMPS BACKGROUND OF THE INVENTION which for proper operation must be continuously l0 heated by an electric current passed through them from auxiliary energizing equipment. A discontinuity in this filament circuit within the lamp itself may result from poor manufacture or from other means such as vibration or rough handling. Such discontinuity results in a lamp of either no performance at all or one that is erratic in operation or of very short life, making it necessary to provide costly, unscheduled replacement. This type of lamp has a pair of end prongs in the cathode cir cuit for plug-in connection to the base of a lamp fixture. The other type of fluorescent lamp commonly used comprises a lamp designated as a single pin lamp and which does not depend on cathodes heated from an external source for its proper operation.

As is well known, fluorescent lamps have wide usage for lighting rooms and outside areas. In almost all instances the lamps are rather difficult to install and remove. In order for the maintenance engineer to determine whether or not the lamp is operative, he must install the lamp in the fixture and then energize the circuit. Such comprises a considerable waste of time particularly in those instances where the fluorescent lamp is high above the floor.

SUMMARY OF THE INVENTION.

According to the present invention and forming a primary objective thereof, an instrument is provided which is capable of testing the operation of fluorescent lamps while the latter are displaced from an operating electric circuit, thus allowing maintenance engineers or the like to test the lamps before installing them in fixtures.

Another object is to provide an instrument of the type described which is capable of testing the operability of both common types of fluorescent lamps,'namely, the type having cathodes in the form of coated wire filaments which must be continuously heated by an electric current from auxiliary energizing equipment and the type which employs a single pin and does not depend on cathodes heated from an external source.

Still another object is to provide an instrument of the type described having a novel housing structure and novel support means and arrangement of components in the housing which make up an oscillator circuit and inductance coil operated by the circuit.

The invention will be better understood and additional objects and advantages will become apparent from the following description taken in connection with the accompanying drawings which illustrate a preferred form of the device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of an instrument for testing fluorescent lamps embodying features of the present invention, a lamp being shown in association with said instrument for testing;

FIG. 2 is an enlarged sectional view of the instrument taken on the line 2-2 of FIG. 1 and showing another manner of testing a lamp, the latter being shown in phantom lines; and

FIG. 3 is a wiring diagram of electrical components in the instrument.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now in particular to the drawings and first to FIGS. 1, 2 and 3, the instrument of the present invention comprises a housing 10 with an open front 12. A threaded cap 14 is mounted on the rearward endof the housing, and upon its removal access can be had to batteries 16 in a battery compartment 17 of the housmg.

Supported transversely in the housing at the forward i end of the battery compartment 17 is a first disc 18 of electrically non-conductive material which supports a plurality of circuit elements, to be described, forming a high frequency electrical oscillator circuit including a tank coil 20. Disc 18 may be secured in place in the housing by any suitable means such as by a press fit, by adhesive, or other means. The tank coil 20 is formed of bare copper wire and is open at its outer end. Its internal diameter is capable of allowing an end of a fluorescent lamp L to be inserted freely thereinto. FIG. 2 shows an end portion of a lamp inserted in the tank coil, the lamp being shown in phantom lines. As will be more apparent hereinafter, the lamp to be tested by inserting it in the tank coil 20 is of the type having a pair of contact prongs P.

Secured transversely in the housing 10 forwardly of the disc 18 is a second disc 24 of electrically non-conductive material which supports a socket member 25 arranged for plug-in engagement thereby of the prongs P of fluorescent lamps. Disc 24 is seated on a shoulder 26 in the housing and is secured to the disc 18 by rivets 27 which also pass through and secure the socket member 25 to the disc 24. Spacers 28 are provided on the rivets 27 between the two discs 18 and 24 to maintain the discs a selected distance apart so that electrical components can be mounted on the disc 18, and be protected in thearea between the two discs. Tank coil 20 has lead portions 29 extending through the disc 18 for connection to other components of the high frequency electrical oscillator circuit, to be described.

Mounted on the housing 10 is a normally open push button switch 30 which is adapted to be manipulated by the same hand that grips the housing, similar to a flashlight, whereby a person can operate the instrument with one hand while holding a fluorescent tube in close proximity to the instrument with the other hand. Switch 30 is disposed in the circuit between the batteries 16 and the tank coil 20. Thus, the circuit to said tank coil is normally open but it can be closed by closing the switch 30. As will be more apparent hereinafter, socket member 25 is also in the circuit between the batteries 16 and the tank coil and normally causes such circuit to be open, such socket being connected in the circuit at a point disposed between the leads 38 and 40 to the push button switch 30 so as to be capable of by-passing said switch. When the socket member is engaged by a two prong type lamp, however, the circuit through the filament of the lamp closes the circuit through socket member 25 if the filament is good for energization of the tank coil 20. The circuit to the tank coil is therefore closed only if the filament circuit of the lamp being tested is intact. A resilient protective layer 31 is disposed between the disc 18 and the batteries for protection of the disc 18. i

With reference to FIG. 3, which shows the wiring diagram of the present circuitry, a pair of lead wires 32 and 34 extend from the positive and negative sides of the batteries 16. Connected in the wire 34 is a diode 36 which protects the circuit against a reversing polarity from the battery. Push button switch 30 and socket member 25 are connected into wire 34, with the leads 38 and 40 to the switch being connected on opposite sides of the socket member 25 whereby as stated above push button switch is operable to close the circuit to the tank coil 20 but if a lamp is plugged into the socket member 25 it by-passes the switch 30 and closes the circuit to the tank coil 20 through its filament circuit, provided of course the circuit through the filament is intact.

The high frequency oscillating circuit also includes a transistor 42 together with a pair of by-pass condensers 44 and 46 and a pair of bias resistors 48 and 50 which establish the base bias on the transistor for proper operation. There is also included a pair of radio frequency chokes 52 and 54 which localize the high frequency current.

The emitter circuit of the transmitter also includes a pair of condensers 56 and 58 to block DC. and provide feedback, and also included in such circuit is a diode 60 and resistor 62 for-temperature compensation. Also included in the circuit across the coil 20 is a tuning condenser 64. Tank coil 20 has a selected number of turns and input energy from the circuit to produce a necessary induction output to light fluorescent lamps merely by being disposed in close proximity thereto. An induction output of 52 megacycles has been found to'be satisfactory for the intended purpose. The circuitry to produce the high frequency oscillating circuit is of well known arrangement and is therefore not described in detail. The arrangement of the push button switch and the socket member 25 in such a circuit and their control of the tank coil however comprise a novel combination.

By use of the solid state circuitry and the components described, a portable high frequency electrical oscillator is provided which through inductive effect from the coil will cause a fluorescent lamp to light up when in close proximity to the coil. In the two prong type of fluorescent lamp, the lamp is moved endwise into the tank coil 20 and plugged into the socket member 28, FIG. 2. If the filament circuit in the lamp is intact, the circuit to the tank coil is completed through the socket member, and the inductive effect in said coil causes the lamp to light to indicate to the operator that the lamp is in good condition. If the filament circuit, or the gas content, is not proper, the lamp will not light and the operator has indication of a non-functional lamp before he goes through all the trouble of placing it in the fixture. If a lamp lights, the color and range of illumination will indicate the quality of the gas filling.

To test the other type of fluorescent lamp, namely,

the type of. lamp which utilizes a single pin and which does not depend on the cathodes being heated from an external source for their proper operation, FIG. 1, the instrument is merely moved endwise into close proximity with a fluorescent lamp intermediate the ends of the latter. Push button switch 30 is then closed, to energize the tank coil. If the lamp is good, it will light. If the lamp does not light, it is an indication that the gas content is defective. The extent of defectiveness can be determined by the color of light emitted from the lamp.

According to the present invention, it is apparent that fluorescent lamps can be tested before being installed in a fixture for saving considerable time. Or, if it is desired that lamps be tested which are already installed, such can be accomplished without energizing the circuit to the lamp. In this latter case, the lamps can be tested without producing a glare in the operators eyes. The instrument, being portable, is convenient in its use both in the field as well as in the shop or factory. In those cases where one key lamp will make others in a group inoperative, the faulty lamp is readily found by use of the present instrument. Also, it is apparent that the instrument can be used to determine if trouble exists in a circuit in that if a lamp will not light in the fixture but will light under the influence of the present instrument, it is almost apparent that the circuit is faulty.

It is to be understood that the form of my invention herein shown and described is to be taken as a preferred example of the same and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of my invention or the scope of the subjoined claims.

Having thus described my invention, 1 claim:

1. An instrument for testing fluorescent-type lamps by lighting operative ones of said lamps even though the latter are isolated from the usual energizing electrical circuit, comprising a housing having forward and rearward ends, electrical means in said housing includ-- ing a high frequency electrical oscillator, a tank coil in the oscillator circuit producing an induction output capable of lighting a lamp, said tank coil having an open end arranged to receive an end portion of a fluorescent lamp for saidtesting, and socket means having contacts in said oscillator circuit normally opening the circuit to said oscillator but being arranged to close the circuit to said oscillator when a tube is plugged therein, said socket means being supported in said housing in a position for plug-in engagement by a tube which is received in said tank coil for testing the tube.

2. The instrument of claim 1 including a push button switch in said electrical circuit arranged to by-pass the circuit through said socket means when operated whereby to close the circuit to said oscillator without plug-in engagement of a lamp in said socket.

3. The instrument of claim 1 wherein said housing has a battery compartment at one end, first support means intermediate said battery compartment and said tank coil for supporting electrical components in said housing, and second support means intermediate said first support means and said tank coil for supporting said socket means. 

1. An instrument for testing fluorescent-type lamps by lighting operative ones of said lamps even though the latter are isolated from the usual energizing electrical circuit, comprising a housing having forward and rearward ends, electrical means in said housing including a high frequency electrical oscillator, a tank coil in the oscillator circuit producing an induction output capable of lighting a lamp, said tank coil having an open end arranged to receive an end portion of a fluorescent lamp for said testing, and socket means having contacts in said oscillator circuit normally opening the circuit to said oscillator but being arranged to close the circuit to said oscillator when a tube is plugged therein, said socket means being supported in said housing in a position for plug-in engagement by a tube which is received in said tank coil for testing the tube.
 2. The instrument of claim 1 including a push button switch in said electrical circuit arranged to by-pass the circuit through said socket means when operated whereby to close the circuit to said oscillator without plug-in engagement of a lamp in said socket.
 3. The instrument of claim 1 wherein said housing has a battery compartment at one end, first support means intermediate said battery compartment and said tank coil for supporting electrical components in said housing, and second support means intermediate said first support means and said tank coil for supporting said socket means. 